The invention relates generally to defibrillation electrodes and particularly to epicardial defibrillation electrodes having conductive dirk members to penetrate the epicardium.
To perform defibrillation with the voltages and energies that are available from present implantable devices it is critical that the resistance of the defibrillation electrodes be as low as possible. Although various types and configurations of electrodes have been proposed and used for defibrillation, epicardial patch electrodes continue to be the most effective defibrillation electrode structures. However, a shortcoming of the epicardial patch is that a large portion of the voltage may not effectively penetrate into the myocardium. For example, animal studies have shown that up to 70% of the electrode potential is lost in the first few millimeters of the heart.
One prior art approach at lowering the electrode impedance is the use of relatively large electrode structures which are contoured to the shape of the heart and stitched in place. A drawback of these structures is that with sufficiently large patches they may be positioned too close to each other. As a result, the defibrillation current may take the shortest route from the edge of one patch to that of the adjacent patch causing the beneficial defibrillation current to the heart to be shunted away.
Although various epicardial defibrillation electrode configurations have been utilized and proposed, they have generally been designed to be positioned against the epicardium or to be implanted subcutaneously a distance from the heart. The object of the present invention is to provide an epicardial defibrillation electrode having outwardly extending dirks which penetrate the epicardium and contact the myocardium.
A further object is to provide dirk based epicardial electrode devices which utilize support members which aid in the positioning and implantation of the electrodes. Another object of the invention is to provide epicardial electrode devices having a plurality of outwardly extending dirk members and circuitry in communication therewith and which may be utilized for pacing, sensing and defibrillation.